Monitor distance by task and screen size
Reading text is different from keeping a whole display in view. Start with the task, then choose the screen type if needed. Pixel resolution alone cannot set a comfortable viewing distance: text size and scaling also matter.
Method and limitations
Reading: CCOHS, 40–74 cm (about 15.7–29.1 in). Whole-screen viewing: DGUV Table 6, p. 39, 22-inch widescreen → 90 cm; 24-inch widescreen → 100 cm. Direct lookup; no interpolation or resolution-based formula. Unit conversion: 1 in = 2.54 cm exactly (NIST), rounded to one decimal place.